1. Field of the Invention
This invention relates to switching mechanisms, and more particularly, to a switching mechanism which utilizes electromagnets for switching purposes.
2. Description of the Prior Art
In a typical prior art coaxial switching mechanism 8, (FIG. 1), as manufactured by Teledyne Microwave, Inc., a switch body 10 includes a lower body portion 12, an upper body portion 16 fixed to the lower body portion 12, and a cap 13 fixed to the lower body portion 12 and defining a cavity 14 within which the upper body portion 16 is positioned. Mounted to the upper body portion 16 are electromagnets 18, 20, the electromagnet 18 including an iron core 22 within a coil 24, and the electromagnet 20 similarly including an iron core 26 within a coil 28. An iron plate 30 is fixed to the body 16, and the portion 30A of the iron plate 30 connects the top portions 22A, 26A of the cores 22, 26. A permanent magnet 32 is connected to the iron plate 30 between the coils 24, 28, this permanent magnet 32 having, for example, the north pole thereof in contact with the plate 30 to induce a north pole in the plate 30.
The upper body portion 16 defines an internal cavity 34 into which respective portions 22B, 26B of the cores 22, 26 extend. Pivotally mounted to the body portion 16 within that cavity 34 is a soft iron rocker 36 that is pivoted at its center directly below the lower magnet pole (in this embodiment the south pole) of the permanent magnet 32.
With the south pole of the permanent magnet 32 adjacent the rocker 36, a continuing south pole is induced in the rocker 36.
The rocker 36 is movable to a first position, shown in FIG. 1, whereby an end portion 36B thereof is adjacent and in contact with the portion 26B of the core, while the other end portion 36A thereof is removed from the end portion 22B of the core 22. The rocker 36 is movable to a second position wherein the end portion 36B is removed from the end portion 26B of the core 26, while the end portion 36A is brought adjacent to and into contact with the end portion 22B of the core 22.
With the rocker 36 in its first position (FIG. 1), a portion 38A of actuator spring mechanism 38 fixed to the rocker 36 acts on a dielectric rod 40 which in turn urges a conductive reed 42 (against the force of a spring 44) into contact with conductors 46, 48. Meanwhile, the spring mechanism portion 38B is removed from the dielectric rod 50 in association with the other conductive reed 52, so that reed 52 is moved by spring 54 to result in electrical connection not being provided between the conductors 48, 56.
With the rocker 36 in its second position, the spring mechanism portion 38B causes the reed 52 to be moved to provide electrical connection between the conductors 48, 56, while the reed 42 is removed from conducting between the conductors 46, 48.
If, for example, current is applied to the coil 28 to induce a north pole at the portion 26A of the core 26 and a south pole at the portion 26B thereof adjacent the rocker 36, the north pole of the core 26 and the north pole of the plate portion 30A will supplement each other (no current flowing through the coil 24 of the electromagnet 18), to produce a strong north pole at the portion 22B of the core 22. Thus, there will be a strong attracting force between the end portion 36A (south pole) of the rocker 36 and the portion 22B (north pole) of the core 22, while there will be a repelling force between the end portion 36B (south pole) of the rocket 36 and the end portion 26B (south pole) of the core 26. This provides a moment of rotation applied to the rocker 36, and as it moves from its first toward its second position, the spring 44 moves the reed 42 out of contact with the conductors 46, 48, while the spring mechanism portion 38B moves the reed 52 against the force of the spring 54 into contact with the conductors 48, 56.
To switch back to the original position (shown in FIG. 1), current is cut off from the coil 28 of the electromagnet 20 and current is applied to the coil 24 of the electromagnet 18 to provide the reverse action.
Achievement of such switching requires only a momentary current pulse on an appropriate coil to complete each switching operation. However, heretofore, current has remained on at the coil last activated, until it is applied to activate the other coil, whereupon current is cut off from the first coil.
An activated coil is therefore subject to being heated up as long as the current remains therethrough, whereby the resistance of that coil may be increased to the stage where the voltage and current available are no longer able to provide sufficient magnetic force to perform the switching operation when required. This detrimental heat condition is increased by operating the switching mechanism in a hot environment, as is often required.